Conventional synthetic jets are periodic jets generated by pushing and pulling a fluid through an orifice of an actuator. While the actuator reciprocatingly acts, the fluid would be revolvingly oscillated, and be sucked into or jetted out from the actuator due to the pressure variation therein. Since the mass flux of the fluid sucked into the actuator is equal to that of the fluid jetted out, i.e. a time-mean mass flux of the oscillated fluid through this orifice is zero, the synthetic jets is so called as “Zero-Net-Mass-Flux jets” in early days. Other common expressions for such a generation of jets are “Suction and Blowing” and “Oscillatory Blowing”.
Technically speaking, synthetic jets are generated by a periodic Zero-Net-Mass-Flux actuator, which can be arranged in various types. Please refer to FIG. 1(a), which illustrates the structure of a conventional Zero-Net-Mass-Flux actuator. The conventional Zero-Net-Mass-Flux actuator 1′ has a sealed chamber 10′ formed by a surrounding wall 11′. The surrounding wall 11′ has an input orifice 113′, at least one jetting element 115′, such as an orifice or a nozzle, on one side of the chamber 10′, and a diaphragm 12′ (or a piston) on the other end of the chamber 10′ for sealing. Mechanical energy for forcing the diaphragm 12′ is supplied to the Zero-Net-Mass-Flux actuator 1′ through various means, and the diaphragm 12′ is sorted accordingly, such as the electromagnetic diaphragm, the electrodynamic diaphragm, the piezoelectric diaphragm, the electrostatic diaphragm, the thermopneumatic diaphragm, the bimetallic diaphragm, the electrohydrodynamic diaphragm, the shape memory material diaphragm and the pneumatic diaphragm. In short, a feeding from any mechanical energy source will keep the diaphragm 12′ reciprocatingly acting.
Please refer to FIGS. 1(b) and 1(c), which illustrate the actions of the conventional Zero-Net-Mass-Flux actuator 1′. The diaphragm 12′ is actuated toward the U direction during the up-stroke. The pressure inside the chamber 10′ is hence getting lower, and a fluid 2′, which is originally outside the Zero-Net-Mass-Flux actuator 1′, would be sucked into the chamber 10′ through the input orifice 113′ for the pressure drop and hence forms a working fluid. The jetting element 115′ is closed at that time, as shown in FIG. 1(b).
Referring to FIG. 1(c), accordingly, while during the back-stroke, the working fluid 3′ in the chamber 10′ is pushed because the diaphragm 12′ is actuated toward the D direction. The pressure inside the chamber 10′ will be increased, and the working fluid 3′ sucked into the chamber 10′ during the up-stroke is hence pushed. The working fluid 3′ is pushed and jetted out through the input orifice 113′ and the jetting element 115′, and the jets are generated thereby.
Since the sucked working fluid in the up-stroke would be completely jetted out in the back-stroke, i.e. the mass flux of the sucked working fluid is equal to that of the jetted working fluid, the net mass flux of the working fluid, which flows in and out of the Zero-Net-Mass-Flux actuator 1′, is zero in each of the reciprocatingly acting process of the diaphragm 12′.
On the other hand, if the working fluid flows in and out of the actuator through different jetting elements, the mass flux of the sucked working fluid would be hence different from that of the jetted working fluid, which may be resulted from changing the structure and the arrangement of the jetting elements of the actuator. For the respectively different mass fluxes of the sucked working fluid and the jetted working fluid, the net mass flux would not be zero. Non-Zero-Net-Mass-Flux jets would be generated therefore.
Based on the basic principles involved in the fluid mechanics, for considering the limitation of the Reynolds Number of the fluid, it needs a quite complicated arrangement of a pipe structure and moving parts for the fluid flows mixing controlling, the fluid field controlling, such as the fluid stream vectoring and the turbulence controlling, and for generating the fluid for a small-scale cooling system conventionally. This may further restrict the application of the conventional fluid in the small-scale system as a result.
However, when the synthetic jets are jetted through a jetting element, a vortex will be accordingly generated in the shear layer thereof. The fluid surrounding to the actuator will be further rolled by the vortex to induce an enhancement of the vortex. Besides, due to the simpler structure, the actuator for generating the synthetic jets is more beneficial for the applications in a small-scale system. Therefore, the synthetic jets are respectably potential for applications in the micro fluid mixing and the fluid field precisely controlling, and are broadly applied for the relevant applications.
Since the mass flux of the working fluid sucked into the actuator is equal to that of the working fluid jetted out during the reciprocatingly action of the Zero-Net-Mass-Flux actuator, the efficiency of the heat transfer would be slashed and the actuator will fail in cooling if the temperature difference between the fluids sucked in and jetted out is extremely small. Therefore, if a simpler method and device for generating the Non-Zero-Net-Mass-Flux fluid is provided, the temperature difference between the fluids sucked in and jetted out is able to be increased by repeatedly injecting a fresh fluid outside the actuator thereto. By the increased temperature difference and the enhancement of the fluid field, the Non-Zero-Net-Mass-Flux fluid can not only be applied for the conventional fluid field controlling, but also effectively improves in solving the thorny problem of the heat, which is generated by the high power electrical device.
Based on the above, in order to overcome the drawbacks in the prior art, a double-acting device for generating a Non-Zero-Net-Mass-Flux fluid and a cooling method therefor are provided in the present invention.